US forces apologised on Wednesday for dropping leaflets in northern Afghanistan depicting a dog with a Quranic verse written across its body — an image highly offensive to Muslims.

A photo of the alleged leaflet circulating on social media shows a lion chasing a white dog — the same colour as the Taliban's flag — with the holy verse “There is no God but Allah, and Mohammad is the messenger of Allah” superimposed on its body.

Dogs are seen as unclean creatures in the Muslim culture and the association of Islam with a canine in deeply religious Afghanistan has angered many people.

“Take back your freedom from these dogs. Help the security forces eliminate these enemies. Take back your freedom and ensure your security,” the leaflet says.

NATO forces frequently drop leaflets over large swathes of Afghanistan in an effort to persuade locals against supporting insurgents.

Social media users condemned the disrespectful design on the leaflets, which were dropped in Parwan province.

“Death to infidels, death to their servants,” one user posted on Facebook.

Another wrote: “They do this in a country with a 99.9% Muslim population."

Major General James Linder, who heads the US and NATO special operations forces in Afghanistan, apologised for the leaflet design which he said was an “error”.

“The design of the leaflets mistakenly contained an image highly offensive to both Muslims and the religion of Islam,” Linder said in a statement. “I sincerely apologise. We have the deepest respect for Islam and our Muslim partners worldwide.”

An investigation into the incident is underway, said a spokesman for the special operations forces at Bagram Airbase in Parwan, America's largest base in Afghanistan.

He refused to release a copy of the leaflet.

Hassiba Efat, a member of the Parwan provincial council, told AFP that the leaflets were "very offensive to Islam”.

He added: “The people in the villages are angry about it but so far we have had no reports of any demonstrations. They [foreign forces] have apologised and promised to collect as many of the leaflets as possible.”

It is not the first time US forces have caused offence in Afghanistan where they have spent the past 16 years waging war against the Taliban.

In 2012, US troops set fire to copies of the Koran, sparking days of protests in which about 40 people died.